1. General Model Information

Name: 2DLEAF

Acronym: 2DLEAF

Main medium: air+terrestrial
Main subject: biogeochemistry
Organization level: organs
Type of model: partial differential equations (finite elements,2D), ordinary differential equations
Main application:
Keywords: gas exchange, leaf photosynthesis, transpiration, CO2, stomatal regulation, steady state, transport, Galerkin finite element numerics, Farquhar/Tenhunen model,

Contact:

Dr. Ludmila B. Pachepsky
USDA, ARS, Remote Sensing and Modeling Laboratory,
BARC-West, Bldg. 007, Rm 008
10300 Baltimore Ave, Beltsville, MD 20705
USA
Phone: (+1-301) 5046042
fax: (+1-301) 5045823
email: lpachepsky@asrr.arsusda.gov

Author(s):

Dr. Ludmila B.Pachepsky and Basil Acock

Abstract:

The model simulates

transport of CO2 and water vapor in the intercellular spaces and in the boundary layer adjacent to a leaf,
fluxes of CO2 across the surface of cells due to assimilation, and
fluxes of water vapor from the cell surfaces due to a difference between cellular and intercellular water vapor pressure.

Gas transport is considered as a two-dimensional flow. A submodel describes the effects of external factors on stomatal aperture. Carbon dioxid assimilation by mesophyll cells is simulated using a model based on the kinetics of a single enzym, Rubisco (Farquhar/Tenhunen model).
The model purpose is to predict the leaf photosynthesis and transpiration for various environmental conditions for plants adapted and non-adapted to elevated CO2 atmosphere. Modeling gas diffusion within a leaf and in the boundary layer adjacent to a leaf surface seems to be a promising approach that excludes lumped transport parameters and uses the measurable geometric parameters of leaf anatomy.
The model considers stationary two-dimensional transport of serveral gases in the air-filled leaf domain and the boundary layer near the leaf surface. The governing equations of gas transport are solved numerically to obtain spatial distributions of the gas contents within the leaf cross-section domain. The Galerkin finite element method with linear basis functions and triangular elements is used.

II. Technical Information

II.1 Executables:

Operating System(s): DOS, Windows95 The executables are free available upon request from L.B. Pachepsky.

II.2 Source-code:

Programming Language(s): Fortran, is not available

II.3 Manuals:

Currently available upon request from L.Pachepsky. Manual for Win95 will be available in a month.

II.4 Data:

III. Mathematical Information

III.1 Mathematics

III.2 Quantities

III.2.1 Input

III.2.2 Output

IV. References

Pachepsky, L.B., Haskett, J.D., Acock B. (1995): A two-dimensional model of leaf gas exchange with special reference to leaf anatomy.
J.Biogeogr., 22: 209-214.
Pachepsky, L.B., Haskett, J.D., Acock B. (1996): An adequate model of photosynthesis. 1. Parametrization, validation and comparison of models.
Pachepsky, L.B., Acock B. (1996): A model 2DLEAF of leaf gas exchange: development, validation, and ecological application.
Ecological Modelling, 93, 1-18.

V. Further information in the World-Wide-Web

poster presented at the ISEM worldwide meeting at baltimore, 2.-6. Aug. 1998 Users in Europe may prefer: local mirror (Europe)
EFFECT OF LEAF INTERCELLULAR SPACE GEOMETRY ON PHOTOSYNTHESIS AND TRANSPIRATION RATE: EXPERIMENTS WITH THE MODEL 2DLEAF.
L. Pachepsky and B. Acock
EXCHANGE: NUMERICAL EXPERIMENTS WITH THE 2DLEAF MODEL.
L. Pachepsky and B. Acock
CIESIN information on 2DLEAF

VI. Additional remarks

The 2DLEAF model was applied to study

the effect of stomatal density on photosynthesis and transpiration rates in current and elevated CO2 atmosphere;
the effect of leaf internal structure on transpiration and photosynthesis rates;
to estimate the anatomical, stomatal, and biochemical components of differences in photosynthesis and transpiration of wild and transgenic tobacco leaves.

Input data:

Photosynthesis and transpiration rates;
Leaf cross-sections;
Stomatal density.

The model was parameterized and validated for tomato, soybean, tobacco, and cotton leaves. Image analysis software (like SigmaScan) is needed for an adequate schematization of the leaf internal structure.

Last review of this document by: Dr. L. Pachepsky ,22.01.97
Status of the document:
last modified by Tobias Gabele Wed Aug 21 21:44:38 CEST 2002